Centrifugal basket



1966 w. GRIESELHUBER ETAL 3,283,910

CENTRIFUGAL BASKET I Filed April 2, 1964 5 Sheets-Sheet 1 INVENTORS WILLIAM GRIESELHUBER CHARLES B-SAZAVSKY A RNEY Nov. 8, 1966 w. GRIESELHUBER ETAL CENTRIFUGAL BASKET 5 Sheets-Sheet 2 Filed April 2, 1964 INVENTORS WILLIAM GRIESELHUBER BYCHARLES B. SAZAVSKY A RNEY 1966 w. GRIESELHUBER ETAL 3,283,910

CENTRIFUGAL BASKET Filed April 2, 1964 5 Sheets-Sheet 5 Fig.3

INVENTORS WILLIAM GRIESELHUBE CHARLES B. SAZAVSKY ATT NE) United States Patent 3,283,910 CENTRIFUGAL BASKET William Grieselhuber and Charles B. Sazavsky, Hamilton,

Ohio, assiguors to The Western States Machine Company, Hamilton, Ohio, a corporation of Utah Filed Apr. 2, 1964, Ser. No. 356,763 4 Claims. (Cl. 210380) This invention relates generally to centrifugal baskets, and is particularly directed to improvements in the baskets of continuous centrifingals, for example, of the kind employed for separating syrup of liquid from the solid sugar crystals in the process of refining sugar.

In some existing continuous centrifugals, the basket, which is of frusto-conical form and rotated about its vertical axis, has its small diameter end lowermost, and the inner surface of the basket is constituted by a perforated screen. When the material to be centrifuged, for example, massecuite or a slurry of sugar crystals and liquid or syrup, is continuously introduced into the bottom or diameter end of the rotated basket, centrifugal force causes such material to travel upwardly over the perforated screen and the liquid or syrup is filtered therefrom and passes radially outward through the perforations of the screen while the solids are carried over the upper rim or edge of the basket. In order to prevent passage of the smallest grains or crystals of the solids through the screen, the latter must be very fine and provided with Ini-nute perforations, in which case difliculties are experienced in adequately supporting the screen againstthe substantial centn'fugal forces acting thereon while avoiding undesirable blocking of the perforations of the screen, and in providing adequate draining off of the liquid that has filtered through the screen.

Accordingly, it is an object of this invention to provide a centrifugal basket, particularly for continuous centrifugals, which has a wall structure affording ideal support for the fine perforated screen along closely spaced lines, thereby leading to. relatively longer life of the screen, and effecting efiioient draining off of liquid filtering through the screen so as to make possible the desired degree of separation of the liquid and solid phases of the massecuite or other feed material.

Another object is to provide a centrifugal basket of the described character with improved means for securing the fine perforated screen within the basket, and which particularly avoids any interference with the passage of the sugar crystals or other solids over the top rim of the basket.

A further object is to provide a centrifugal basket of the described character constituted by a unitary metal wall of frusto-conica-l form and a perforated screen of complementary form overlying the inner surface of such wall, and wherein the wall has a multiplicity of annular grooves recessed circumferentially in its inner surface and drain holes extending through the wall, with such grooves being dimensioned and separated to define circumferential ribs therebetween which, at their tops, from closely spaced lines of support for the screen between which drainage of the liquid filtering through the screen is effected, and the drain holes being located to efli-cient- 1y drain off the liquid from the grooves while avoiding undesirable weakening of the unitary metal wall.

In accordance with an aspect of this invention, each of the drain holes is cut through a related one of the ribs at their inner surface of the wall so as to communicate with and lead liquid radially away from the two grooves adjacent such rib, and further the drain holes are preferably arranged in circumferential tiers extending along alternate n'bs of the wall so that unbroken ribs remain between adjacent tiers of drain holes, and the drain holes ice in each of the tiers are staggered :circumferentially with respect to the drain holes of the next adjacent tiers to dispose the drain holes of alternate tiers in rows extending along lgener-atrices of the frusto-conica1 wall, whereby all of the grooves are in communication with drain holes and yet undue weakening of the wall by the drain holes is avoided. By virtue of the presence of unbroken ribs between the pairs of grooves drained by holes out through the intervening ribs, and of the location of the screen on the top surfaces of the ribs, the liquid filtered through the screen is prevented from climbing along the inside of the basket wall and is confined substantially to, and discharged from the grooves receiving the "liquid from the screen.

In accordance with another aspect of the invention, the lower side of each groove, that is the side facing in the direction of increasing diameter of the conical surface defined by the tops of the ribs, and such conical surface enclose an acute angle, while the upper side of the groove and the conical surface close an obtuse angle for encouraging the draining into the grooves of liquid filtered through the screen. In a preferred embodiment of the invention, the lower side of each groove is inclined upwardly in the radially outward direction, while the upper side of the groove is in a horizontal plane.

A further feature of the basket embodying this invention is the provision of a clamping ring having a frustoconical outer surface portion and dimensioned to fit within the relatively small diameter end portion of the frustoconical wall, with means for drawing the ring axially relative to the wall in the direction away from the large diameter end of the latter so that the screen is clamped to the wall between the clamping ring and the adjacent lower end portion of the wall and the remainder of the screen is merely urged radially against the wall by centrifugal force applied to the screen during rotation of the basket.

The above, and other objects, features and advantages of the invention, will be apparent in the following detailed description of an illustrative embodiment thereof which is to be read in connection with the accompanying drawings forming a part hereof, and wherein:

FIG. 1 is a fragmentary, vertical sectional view of a continuous centrifugal having a basket in accordance withan embodiment of this invention;

FIG. 2 is an enlarged, fragmentary top plan view of the centrifugal basket with the screen of the latter being partly broken away to expose the underlying inner surface of the basket wall;

FIG. 3 is a sectional view taken along the line 3-3 on FIG. 2; and

FIG. 4 is a further enlarged fragmentary sectional view corresponding to a portion of the structure shown on FIG. 3.

Referring to FIG. 1 in detail, it will be seen that a centrifugal basket 10 embodying this invention is there shown as part of a continuous centrifugal 11 operative to separate the liquid and solid phases or constituents of a mixture thereof, for example, as in the separation of the syrup or liquid from the sugar granules during the refining of sugar. The continuous centrifugal 11 has a housing 12 with a framework or base 13 in the housing supporting an annular horizontal plate 14. Upstanding walls 15 and 16 extend along the inner and outer peripheries of annular plate 14 to define a liquid collection chamber 17 located above plate 14 between walls 15 and 16, and a solid collection chamber 18 defined between wall 16 and the outer wall of housing 12. At least three equally spaced apart brackets 19 (only one of which appears on FIG. 1) depending from plate 14 adjacent the inner periphery of the latter and carry amounts 20 by which a bearing housing 21 is yieldably supported. The bearing housing 21 is centered with respect to the inner peripheral wall 15 and contains suitable bearings (not shown) which rotatably support a vertical shaft 22. The lower end of shaft 22 has a sheave 23 secured thereon which is driven by a belt 24 from a suitable electric motor (not shown). The upper end of shaft 22 projects from bearing housing 21 and has a flange 25.

The basket has a hollow, generally cylindrical hub 26 extending over bearing housing 21 with radial clearance therebetween. The upper end of hub 26 is formed with an inwardly directed radial flange 27 seating on flange 25 of shaft 22 and being secured thereto, as by bolts 28. The lower end of hub 26 has an outwardly directed radial flange 29 surrounded by the wall 15, with radial clearance therebetween.

In accordance with this invention, the basket 10 includes a unitary metal wall 30 of frusto-conical form having its relatively small diameter end at the bottom and integral with a cylinder-extension 31 which is secured, as by bolts 32, to -the periphery of flange 29, as shown on FIG. 1. The upper edge of frusto-conical wall 30 has an integral rim or outwardly directed extension 33, and the wall 30 and its extensions 31 and 33 are formed as a unitary casting, preferably of stainless steel.

The casting is suitably machined so as to have a multiplicity of annular grooves 34 recessed circumferentially in the inner surface of wall 30. The entire inner surface of frusto-conical wall 30 is provided with grooves 34 with the exception of relatively narrow, smooth annular portions 35 and 36 provided adjacent the lower and upper margins of the inner surface of the wall, as shown on FIG. 3. The grooves 34 are separated by circumferential ribs 37 integral with the wall 30 and the tops 38 of which define elements of a common conical surface that also includes the smooth annular portions 35 and 3d at the bottom and top of the inner surface.

Resting against the tops 38 of the ribs 37 and the smooth annular surface portions 35 and 36 is a perforated screen 39 having a form corresponding to that of the common conical surface defined by the tops 38 and the surface portions 35 and 36. The screen 39 is held in position against wall 30 exclusively by a clamping ring 40 (FIGS. 1 and 3) fitting within cylindrical extension 31 of wall 30 and having an outwardly flaring upper edge portion 41 with an outer surface of frusto-conical form having the same cone angle as the lower smooth surface portion 35 for engaging the lower edge portion of screen 39 therebetween. The clamping ring 40 has an inwardly directed radial flange 42 which is drawn downwardly toward flange 29 of hub 26, as by screws 43, thereby securely clamping the lower edge of screen 39 between the upper edge portion 41 of the clamping ring and the smooth surface portion 35 at the bottom of the inner surface of wall 30. The remainder of the screen 39 merely rests against wall 30 and is held against the latter by the centrifugal force acting on the screen during rotation of basket 10.

The massecuite or other mixture of liquid and solids to be separated, is introduced into the centrifugal 11 by means of a feed tube 44 (FIG. 1) discharging into the basket 10 in the region between hub 26 and clamping ring 4!). During rotation of basket 10, the centrifugal force acting on the mixture in basket 10 has a component indicated by the arrow F on FIG. 1, directed upwardly and outwardly along the surface of screen 39. In accordance with known practices, the angle a included between the vertical axis of basket 10 and the generatrices of the frusto-conical inner wall surface of the basket is, for example, between approximately 30 and 35 at a value which nearly corresponds to the friction angle of the solids on the screen. Thus, the force directed upwardly along the surface of screen 39 as a result of the centrifugal action is nearly able to overcome the frictional resistance to the movement of the sugar granules or other solids over the screen surface, and the rate at which the solids are discharged radially outwardly over the upper rim of basket 10, as indicated by the arrows S on FIG. 1, is substantially determined by the rate at which the mixture to be separated is fed to the basket through the feed tube 44. Since the screen 39 is clamped only at its lower edge by the ring 40, there is no obstruction at the upper edge portion of the screen to resist or interfere with the smooth discharge of the solids over the upper rim of the basket.

During the travel of the solids upwardly and outwardly along the inner surface of screen 39, the centrifugal action further causes the separation of the syrup or liquid from the solids and the filtering of the liquid radially outward through the perforations 45 of the screen.

By reason of the thin sheet material employed for the screen 39, it is necessary that the latter he supported along closely spaced apart lines against the loads and centrifugal force applied to the screen during rotation of the basket. It has been found that the screen 39 is adequately supported, and hence afforded a relatively long useful life, when the pitch P (FIG. 4) or distance between the tops of adjacent ribs 37, measured in the vertical direction or parallel to the axis of the basket, is in the range between .187 and .250 inch.

The grooves 34 cut or recessed in the inner surface of frusto-conical wall 30 are dimensioned and shaped, in cross-section, so as to efiiciently receive and drain-off the liquid filtered through the openings 45 of screen 39. As shown on FIG. 4, each groove has a bottom or radially outer surface 46 that is substantially semi-circular in cross-section, with the radius r of curvature of such surface being approximately one-half the depth D of the groove. The upper side 47 of each groove 34, that is, the side of the latter facing in the direction opposed to the direction of increasing diameter of the frusto-conical wall, extends horizontally, that is, in a plane perpendicular to the axis of the basket, so that an obtuse angle b is enclosed between the side surface 47 and the conical surface of screen 39. On the other hand, the lower surface 48 of each groove 34, that is, the side surface of the groove facing in the direction of increasing diameter of the frusto-conical wall, is inclined with respect to the horizontal, that is, from a plane perpendicular to the axis of rotation of the basket, in the direction from the top 38 of the related rib 37 to the bottom. or radially outer surface 46 of the groove. Thus, an acute angle 0 is enclosed between the side surface 48 and the conical surface of the screen, and such angle 0 is smaller than the difference between and the angle b.

By reason of the above described cross-sectional configuration of each groove 34, the top surfaces of the ribs 38 are reduced in Width for minimizing blockage thereby of the filtering of liquid through the openings of screen 39. Further, the upwardly and outwardly inclined lower side surfaces 48 of the grooves, being generally in the direction of the centrifugal action, serve to lead the liquid filtering through the screen toward the bottoms of the grooves for effective drainage, as hereinafter described. It Will also be seen that the horizontal upper side surfaces 47 of the grooves 34, being at an obtuse angle 52 relative to the conical surface of the screen, also direct the liquid radially outward toward the bottoms of the grooves, and thereby discourage the upward leakage of the liquid between the outer surface of the screen 39 and the top surfaces 38 of the ribs 37. It will also be seen that the edges of the top surfaces 38 of ribs 37 are broken or cut away to avoid damage to the screen 39 when the latter is made to bend slightly around such edges by the load or centrifugal force applied to the screen during rotation of the basket.

The liquid received in grooves 34 is drained oif from the :latter through drain holes 49' extending radially through side wall 30 of the basket. As shown particularly on FIG. 4, each of the drain holes 49 is, at its inner end, cut through a related one of the ribs 37 so as to communicate with and lead liquid radially away from the two grooves adjacent such rib. The outer ends of the drain holes 49 open at the smooth outer surface of frusto-conical wall 30 so that the liquid draining outwardly through holes 49 is discharged into liquid collection chamber 17.

As shown on FIG. 1, an annular splash ring 50 may extend downwardly from the upper rim 33 of basket to deflect streams of liquid issuing radially outward from the drain holes 49 in the upper portion of wall 30. A fixed annular baffle 51 may also be mounted within liquid collection chamber 17, as on support rods 52 extending from wall 16, to downwardly deflect the liquid issuing from the drain holes in the lower portion of wall 30. A skirt 53 may also depend from the bottom of wall 30 and be spaced radially outward from the cylindrical extension 31 so as to receive the inner wall therebetween and effectively prevent splashing of liquid from the chamber 17. The liquid collected in chamber 17 is drained from the latter through a discharge pipe (not shown), while the solids discharged radially outward over the rim 33 and into the solids collection chamber 18 are also suitably discharged from the latter.

In accordance with the present invention, undue weakening of the basket wall 30 is avoided and effective draining off of the liquid through drain holes 49 is ensured by arranging the drain holes 49 in circumferential tiers extending along alternate ribs 37 of the wall so that unbroken ribs remain between adjacent tiers of drain holes, as shown particularly on FIGS. 2 and 3. By virtue of the unbroken ribs between adjacent circumferential tiers of drain holes and the seating of screen 39 against top surfaces 38 of the ribs, the liquid filtered through the screen is prevented from climbing along the inside of basket wall 30 and is confined substantially to, and discharged from the grooves receiving the liquid from the screen. Further, the drain holes in each of the circumferential tiers are staggered circumferentially with [respect to the drain holes of the next adjacent circumferential tiers so as to dispose the drain holes of alternate tiers in rows extending along generatrices of the frusto-conical wall 30. By reason of the foregoing arrangement of drain holes 49, all of the grooves 34 are in communication with drain holes 49 for efiective draining of liquid therefrom. However, along any generatrix of the basket having a row of drain holes 49 arranged therealong, adjacent drain holes are cut through ribs which are spaced apart by four times the distance P between adjacent ribs. Further, in the circumferential plane of any of the ribs cut through by drain holes 49, the angular spacing between adjacent drain holes in each tier is equal to twice the angular spacing between the rows of drain holes extending along the generatrices of the firusto-conical wall.

It will be apparent that, since equal numbers of drain holes are provided in all of the circumferential tiers, the spacing between drain holes is smallest in the bottom or small diameter end portion of the basket and increases progressively up to the upper or larger diameter end of the basket. This is particularly advantageous as it provides the maximum open drain hole area adjacent the relatively small diameter end of the basket where approximately 80% of the syrup or liquid is drained from the solids.

Although an illustrative embodiment of this invention has been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiment, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention, except as defined in the appended claims.

What is claimed is:

0 1. A centrifugal basket constituted by a unitary metal 7 wall of frusto-conical form and a perforated screen of complementary form overlying the inner surface of said wall, said wall having a multiplicity of annular grooves recessed circumferentially in said inner surface to a depth sufficient to receive and drain off liquid filtered through said screen, said grooves being separated from one another by circumferential ribs integral with said wall and the tops of which define elements of a common conical surface and are sufficiently close-1y spaced apart to support said screen against the loads and centrifugal force applied to it during rotation of the basket, said wall further having drain holes extending therethrough, each of said drain holes being cut through only alternate ribs so as to communicate with and lead liquid radially away from the grooves adjacent each of said alternate ribs, said drain holes being arranged in circumferential tiers extending along each of said alternate ribs of said wall, the ribs between each two of said alternate ribs being unbroken and free of drain holes to prevent liquid filtered through said screen into said grooves from climbing along the inner surface of the wall, the drain holes in each of said tiers being staggered circumferentially with respect to the drain holes of the next adjacent tiers to dispose the drain holes of alternate tiers in rows extending along generatrices of said frusto-conical wall, whereby all of said grooves communicate with drain holes and undue weakening of said wall by said drain holes is avoided.

2. A centrifugal basket as in claim 1; wherein said tiers of drain holes all have substantially the same number of holes therein so that the drainage capacity per unit area of said frusto-conica-l wall is greatest adjacent the small diameter end of the wall and decreases progressively toward the relatively larger diameter end.

3. A centrifugal basket constituted by a unitary metal Wall of frusto-conical form and a perforated screen of complementary form overlying the inner surface of said wall, said wall having a multiplicity of annular grooves recessed circumferentially in said inner surface to receive and drain off liquid filtered through said screen, said grooves being separated from one another by circumferential ribs having tops defining elements of a common conical surface and against which said screen is seated, said wall further having drain holes extending therethrough, each of said drain holes being cut through only alternate ribs to communicate with and lead liquid radially away from the grooves adjacent each of said alternate ribs, said drain holes being arranged in circumferential tiers extending along each of said alternate ribs of said wall, the ribs between each two of said alternate ribs being unbroken and free of drain holes to prevent liquid filtered through said screen into said grooves from climbing along said inner surface of the wall.

4. A centrifugal basket as in claim 3, said tiers of drain holes all having substantially the same number of holes therein so that the drainage capacity per unit area of said firusto-conical wall is greatest adjacent the small diameter end of the wall and decreases progressively toward the relatively larger diameter end.

References Cited by the Examiner UNITED STATES PATENTS 1,259,048 3/1918 Roberts et al 210380 2,342,973 2/ 1944 Schwarz 210380 2,474,674 6/ 194-9 Holden 14827 X 2,752,043 6/1956 Van Riel 210380' X 2,883,054 4/1959 Sanchez 210380 X 2,973,288 2/1961 Riedel 210380 X 3,151,072 9/1964 Dietzel et al 210380 FOREIGN PATENTS 745,268 2/1933 France.

REUBEN FRIEDMAN, Primary Examiner.

J. DE CESARE, Assistant Examiner, 

1. A CENTRIFUGAL BASKET CONSTITUTED BY A UNITARY METAL WALL OF FRUSTO-CONICAL FORM AND A PERFORATED SCREEN OF COMPLEMENTARY FORM OVERLYING THE INNER SURFACE OF SAID WALL, SAID WALL HAVING A MULTIPLICITY OF ANNULAR GROOVES RECESSED CIRCUMFERENTIALLY IN SAID INNER SURFACE TO A DEPTH SUFFICIENT TO RECEIVE AND DRAIN OFF LIQUID FILTERED THROUGH SAID SCREEN, SAID GROOVES BEING SEPARATED FROM ONE ANOTHER BY CIRCUMFERENTIAL RIBS INTEGRAL WITH SAID WALL AND THE TOPS OF WHICH DEFINE ELEMENTS OF A COMMON CONICAL SURFACE AND ARE SUFFICENTLY CLOSELY SPACED APART TO SUPPORT SAID SCREEN AGAINST THE LOADS AND CENTRIFUGAL FORCE APPLIED TO IT DURING ROTATION OF THE BASKET, SAID WALL FURTHER HAVING DRAIN HOLES EXTENDING THERETHROUGH, EACH OF SAID DRAIN HOLES BEING CUT THROUGH ONLY ALTERNATE RIBS SO AS TO COMMUNICATE WITH AND LEAD LIQUID RADIALLY AWAY FROM THE GROOVES ADJACENT EACH OF SAID ALTERNATE RIBS, SAID DRAIN HOLES BEING ARRANGED IN CIRCUMFERENTIAL TIERS EXTENDING ALONG EACH OF SAID ALTERNATE RIBS OF SAID WALL, THE RIBS BETWEEN EACH TWO OF SAID ALTERNATE RIBS BEING UNBROKEN AND FREE OF DRAIN HOLES TO PREVENT LIQUID FILTERED THROUGH SAID SCREEN INTO SAID GROOVES FROM CLIMBING ALONG THE INNER SURFACE OF THE WALL, THE DRAIN HOLES IN EACH OF SAID TIERS BEING STAGGERED CIRCUMFERENTIALLY WITH RESPECT TO THE DRAIN HOLES OF THE NEXT ADJACENT TIERS TO DISPOSE THE DRAIN HOLES OF ALTERNATE TIERS IN ROWS EXTENDING ALONG GENERATRICES OF SAID FRUSTO-CONICAL WALL, WHEREBY ALL OF SAID GROOVES COMMUNICATE WITH DRAIN HOLES AND UNDUE WEAKENING OF SAID WALL BY SAID DRAIN HOLES IS AVOIDED. 